This invention relates to plastic containers, and in particular, to lids for such containers where the lids have tear-off strips to facilitate the removal of the lids.
In larger plastic containers, such as paint containers capable of holding many litres of paint, it is necessary to provide a strong attachment and good seal between the container and the lid, especially for shipping purposes. Usually, interlocking or inter-engaging flanges are provided on the lid and the upper peripheral edge portion of the container to retain the lid on the container. The difficulty is that the stronger is the engagement between these interlocking flanges, and thus the stronger the attachment of the lid to the container, the more difficult it is to remove the lid when it is desired to do so. Ideally, one would like to have good engagement between the lid and the container for shipping purposes, and some means for relieving or reducing the force of engagement between the lid and the container when it is desirable to remove the lid.
One method of accomplishing the above objectives is to provide the lid with a tear-off strip that contains the lid locking flange that engages the container locking flange. When the lid is on the container, the engaged locking flanges hold the lid securely onto the container. When it is desired to remove the lid, the lid tear-off strip is removed, so there is no longer any locking engagement between the lid and the container. The lid is then easy to remove.
Sometimes, however, after the lid is removed, it is desirable to put the lid back on the container and still have a good seal between the lid and the container. One way of achieving this result is shown in U.S. Pat. No. 4,735,337 issued to John W. Von Holdt. In this patent, the lid outer skirt that contains the locking flange is provided with a zigzag tear line that defines a tear-off strip. The tear line passes repeatedly through the locking flange, so that upon removal of the tear-off strip, portions of the locking flange are removed and only spaced-apart portions of the lid skirt locking flange remain. These remaining portions then provide a lid lock with reduced holding power, so that the lid can be removed and replaced.
Another example of such a lid is shown in U.S. Pat. No. 4,930,656 issued to Henry J. Blanchette. In this Blanchette patent, an intermittent locking flange is provided on the lid peripheral skirt and an undulating annular groove is provided to form a tear-off strip. When the tear-strip is removed, the lid ends up with bendable flaps containing the locking flanges, and these flaps yield to permit easier removal and replacement of the lid.
One difficulty with the prior art Von Holdt and Blanchette patents is that the zig zag or undulating tear-off strips are difficult to remove. The tooling to make the lids shown in these patents is also expensive because of the complex nature of the tear lines. The lid shown in the Blanchette patent is also not as strongly retained on the container as would be desired, because only partial locking flanges are provided on the lid skirt.
In the present invention, a double locking flange is provided to securely hold the lid on the container. One of the locking flanges is totally removed along with the tear-off strip leaving a second, intermittent yieldable locking flange for retention and resealing of the lid on the container.
According to the invention, there is provided a lid for a container, said container having upper and a lower peripheral, annular outwardly disposed container locking flanges, said upper and lower container locking flanges having undersides for locking engagement with the container lid, the lid comprising: a central portion and a peripheral annular skirt adapted to overlie the container locking flanges. The annular skirt defines an annular groove dividing said skirt into a skirt upper portion located adjacent to the container upper locking flange, and a lower tear-off strip portion located adjacent to the container lower locking flange. The skirt upper portion having inwardly disposed intermittent locking flange segments, adapted to engage the underside of the container upper locking flange. The skirt upper portion is also formed with thin membrane windows therein, each said window covered entirely by a thin membrane, said windows positioned circumferentially adjacent to both sides of each locking flange segment and bordering on the annular groove. Also, the tear-off strip portion defines an inwardly disposed locking flange adapted to engage the underside of the container lower locking flange, so that removal of the tear-off strip portion leaves downwardly disposed thin membrane notches, the notches covered entirely by said thin membrane, said notches positioned circumferentially adjacent to both sides of each locking flange segment.